For a number of years, a single wall thermostat has been available for controlling both heating and cooling apparatus supplying either heated or cooled air to a space in which the thermostat is mounted. Such a thermostat might have a single temperature responsive means for operating a switch for both cooling and heating as shown in the Walter E. Edelman et al U.S. Pat. RE. No. 28,676, reissued Jan. 13, 1976, wherein a subbase contains switches for selectively providing the changeover operation to connect the thermostat to control either heating apparatus or cooling apparatus. Other types of thermostats contain separate temperature responsive switch means each controlling heating apparatus or cooling apparatus to provide automatic changeover between the heating and cooling operation such as shown in the Elmer A. Carlson U.S. Pat. No. 2,978,228, issued Apr. 4, 1961. In these thermostats an almost unlimited range of control point adjustment is provided.
Prior art thermostats have had various ways, such as adjustable stops as shown in the Carl G. Kronmiller U.S. Pat. No. 2,729,719, issued Jan. 3, 1966, of limiting the temperature adjustment to some energy conserving level both in the heating and cooling operation. With the advent of a more recognized need to conseve energy, the need for even more sophisticated limiting means for a thermostat setting control point adjustment is recognized.
The present invention provides a thermostat for use for controlling heating and cooling apparatus wherein a control point adjustment in either the heating or cooling range is limited to conserve energy. Furthermore, the thermostat provides for the changeover from heating to cooling operation by means of a less expensive changeover switch apparatus to eliminate the previously used subbase, therefore, a thermostat is available at a lower cost to the consumer. Specifically, the thermostat has a control point adjustment knob which can be adjusted in a cooling range of temperatures or a heating range of temperatures, each of the ranges are limited to provide temperatures for the conservation of energy. The control point adjustment knob is connected to a changeover switch in the thermostat; so that, upon a movement of the control point adjustment knobs from the cooling range to the heating range, the changeover switch is operated. The operation of heating or cooling apparatus when the control point adjustment knob is in the cooling or heating range, respectively, is prevented.